The present disclosure relates to a speaker such as a subwoofer.
Usually, a speaker is composed of: a cone-like diaphragm supported on a frame through an edge; a magnetic circuit that drives the diaphragm; and a damper.
The magnetic circuit includes: a voice coil wound around a voice coil bobbin fixed to an inner circumferential portion of the diaphragm; a plate fixed to the frame; a permanent magnet; and a yoke.
In general, one end side of the damper is fixed to the voice coil bobbin, and the other end side thereof is fixed to the frame. The diaphragm vibrates in such a manner that a current corresponding to an audio signal is applied to the voice coil. Usually, the edge and the damper have functions as suspensions for returning the diaphragm to a regular position.
The diaphragm vibrates in a sound emission direction and a direction opposite thereto. The diaphragm has such a merit of being capable of ensuring a sound pressure significantly to emit a good tone when a stroke of the diaphragm in a vibration direction is not limited. On the other hand, in a subwoofer or the like, which is a form of speaker, a stroke thereof is large, and accordingly, in particular, unless the stroke is limited in the direction opposite to the sound emission direction, then there is a possibility that the voice coil bobbin, the voice coil or the damper may collide with the permanent magnet or the yoke, and sound quality may be deteriorated, or the speaker may be broken.
In Japanese Unexamined Utility Model Application Publication No. S62-32698 (Patent Document 1), a speaker is described, which is configured so that the stroke in the direction opposite to the sound emission direction is limited by providing the frame with a protruding portion that limits deformation of the edge.